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By J. Reyher, R. Bratton, G. Luttrell, B. Li

"Flotation is regarded as the best available method of upgrading minerals and coal fines. However, its efficiency deteriorates rapidly with decreasing particle size. Further, ultrafine concentrates are difficult to be dewatered economically, forcing companies to discard part of the ultrafine materials to impoundments. To overcome these problems, a new method of separating and simultaneously dewatering ultrafine particles has been developed. Following extensive laboratory-scale test work, the process, known as hydrophobic-hydrophilic separation (HHS), has been tested successfully in continuous operations at proof-of-concept (POC)- and pilot-scale tests. The results show that the HHS process is capable of producing high quality clean coal with high recoveries and low moistures. INTRODUCTION Coal preparation plants are designed with up to four parallel processing circuits for treating coarse (> 12 mm), intermediate (12x1 mm) small (1x0.15 mm), and fine (<0.15 mm) particles. The plus 0.15 mm fractions can be effectively cleaned efficiently with gravity separation methods (Wills, 2006). At present, the only commercially viable option for cleaning the finest fraction is froth flotation (Yoon et al., 1999). In flotation, air is dispersed in the form of small air bubbles in a tank in which coal fines are suspended. The small air bubbles selectively collect the hydrophobic coal particles and float to the surface, forming a froth phase which overflows into a launder. As is well known, ultrafine coal particles of less than 30-50 µm are difficult to be collected by the air bubbles, resulting in low recoveries. Furthermore, fine particle flotation suffers from low carrying capacities and poor selectivity due to entrainment problems. (Bethell et al., 2005; Luttrell et al., 2014). In addition, the froth products containing ultrafine coal are difficult to dewater. Mechanical dewatering in general becomes inefficient with decreasing particle size due to small cake porosity and high surface area, resulting in high moistures (Hucko et al., 1988). The cost often becomes prohibitive with particles of smaller than ~45 µm (Bethell et al., 2005). Moreover, the high-moisture products are difficult to handle and incur high shipping costs and lower thermal efficiencies (Honaker et al., 2013)"

Jan 1, 2016

By Edward D. Elkins

CalMat Co. is one of the largest producers of construction aggregates in the United States. The CalMat Reliance plant is located in Irwindale, California, and is situated on an alluvial fan formed by the San Gabriel River. The fan deposits are of Quaternary age and were derived from granitic and metamorphic bedrock exposed in the San Gabriel Mountains to the north. The sediments are poorly sorted and range in size from large boulders to clay size particles. The coarse material is hard and durable and consists of quartz diorite, granodiorite, granitic gneiss, schist and minor amounts of volcanic rock. The matrix is comprised of silty sand with varying amounts of clay. Thin silt and clay lenses occur sporadically throughout the deposit. The clay content of the matrix and the degree of weathering of the coarse material increases with depth. Based on seismic data, the alluvial fan varies from 200 to 400 feet thick and overlies crystalline bedrock. The Reliance plant was constructed in 1971 and 1972. It has a nominal capacity of 1200 to 1400 tons per hour, and typically produces more than three million tons of aggregate products per year. Alluvial fan sediments are mined from a gravel pit situated adjacent to the plant. The material is fed through a mobile, 48- by 60-inch, in-pit jaw crusher, then transported by conveyor to the main plant to be processed. The plant is modern and highly efficient. It has a typical wet and dry circuit and is capable of producing a wide range of aggregate products. To extend the life of the plant, a 9,000 foot conveyor system is being constructed to connect it to a granite quarry operated by Azusa Rock Inc. The quarry is located north of Irwindale, and is 50 percent owned by CalMat Co. The conveyor will be used to export crushed rock from the quarry to Reliance. The existing plant will be modified to process the crushed rock.

Jan 1, 1995

By J. Pinkley

In June of 2002 Hilti North America received the first MSHA permissible approval for usage of a powder actuated tool device in a gassy mine atmosphere. The purpose of this paper is to discuss the implementation of this commonly utilized tool technology in the construction industry, to the underground gassy mining industry over the course of the last 5 years. Prior to June of 2002, underground gassy mining industry had attached materials such as ventilation curtains, power cables, communication cables, signage, and other materials by either manually driving individual spads or nails into the mine roof or rib or by attachment to existing roof bolt bearing plates. The Hilti DX 460 powder actuated tool is portable, durable, and lightweight (4.5 pounds). The Hilti DX 460 powder actuated tool system is powered by Hilti .27 caliber permissible explosive boosters. The energy force of the Hilti .27 booster?s acts on a captive piston principle in the Hilti DX 460 powder actuated tool, that applies the setting force for the direct fastening to the individual fastener chosen for the application by the end user. Each year Hilti can be called upon by MSHA to provide booster materials for re-testing per our Hilti DX PAD 1/00 approval.

Jan 1, 2008

By Wi11iam M. Leaders

Uranium Recovery Corporation was incorporated in the State of Florida in 1968 for the sole purpose of developing a method to economically recover uranium from Florida phosphoric acid. The preliminary laboratory work culminated in the demonstration of the process to United Nuclear Corporation in the spring of 1971. This was quickly followed by a pilot plant program to identify any unusual problems such as those arising from the day-to-day variation which occurs in a fertilizer phosphoric acid plant production system. After two years of pilot plant operation, United Nuclear Corporation purchased controlling interest in Uranium Recovery Corporation and committed several million dollars to the design and construction of the first commercial plant for this purpose in the State of Florida, or anywhere else in the United States, for that matter. After many start-up problems were resolved at the production plant located at the W. R. Grace fertilizer complex near Bartow, sustained production began March, 1971, and has continued to date. We still have some problems to solve but are currently producing sufficient uranium to make shipments to the UF6 converters for preparation of Florida uranium for use in nuclear power plant fuel materials.

Jan 1, 1978

By Ronald P. Geitgey

Pumice and volcanic cinder are volcanic rocks characterized by a cellular structure. They are formed as gases (primarily water) dissolved in molten rock, or magma, exsolve to generate a froth that cools and solidifies into rigid foam. The cells or bubbles are referred to as vesicles and they range in size from a few thousandth of a millimeter to several centimeters. Due to their vesicular character, both pumice and cinder have lower density and higher porosity than most other rock types, and, as the vesicle walls are broken, sharp cutting edges are continually generated. These properties are the basis for their commercial value as lightweight aggregates, insulators, absorbents, and abrasives. There is a certain imprecision in the terminology applied to volcanic products, reflecting to varying degrees the diversity of volcanic rocks, the relative youth of volcanology as a distinct field of study, and customs and practices of commercial trade. In general terms, pumice is light colored (white, gray, pink, pale yellow, or brown) and highly vesicular, usually with vesicle walls that are visibly glassy. Many pumice fragments are light enough to float on water. Pumice is readily cut by steel tools and some can be crushed by hand. Individual pumice fragments may range from 1 or 2 m in one dimension to c1 mm. Commercially, finer fragments are called pumicite or volcanic ash. In volcanology the term ash refers to any fragment c2 mm in size regardless of its composition. Cinder, or scoria, is dark colored (black, red, brown) with thick vesicle walls that appear dull or stony and that may exhibit iridescence. Cinder typically is heavier than pumice and has a higher crushing strength. In volcanology the term scoria refers to dark vesicular material throughout a wide size range while it is common commercial practice to use scoria for larger fragments (usually greater than 2.5 cm) and cinder for smaller fragments. GEOLOGY Composition and Physical Characteristics Most pumice is silicic ranging from 60 to 70% SiO2, that is, dacitic to rhyolitic in composition. Pumice of less silicic composition, including basaltic, occurs but it is less common and does not have extensive commercial use. Scoria and cinder are typically basaltic to andesitic with approximately 50 to 60% SiO2. Pumice and cinder may contain phenocrysts of feldspars and various ferromagnesian minerals that crystallized in the magma prior to eruption. Fragments of rock through which the magma has passed may be entrained in the melt and wall rock may be fragmented and admixed during an explosive eruption. Some scoria particles have lithic fragment cores. Phenocrysts and lithic fragments are relatively unimportant in cinder end uses but their presence may be detrimental in certain pumice products. Pumice typically has vesicles <1 mm in size separated by thin walls. Vesicle shapes include irregular, spherical, elliptical, and elongate to the point of being tubular with a silky appearance (Fig. 1). In some pumices, the vesicles are interconnected making the fragments permeable and highly absorbent; in others the vesicles are isolated forming a highly porous but very impermeable pumice. Floating masses of pumice fragments from the eruption of Krakatoa in 1883 were reported in the Indian Ocean for up to two years after the eruption. Vesicles in cinder are larger and range from spherical to highly irregular in shape with much thicker walls and abundant interconnections. Scoria and cinder are typically heavier, porous, and do not float. Density and hardness of pumice must be expressed precisely to avoid confusion. Density may refer to the glass itself, the apparent density of the vesicular pumice particle, or the bulk density of pumice in a deposit or in a product. Pumice glass has a specific gravity of 2.5 or more depending on its composition. Pumice fragments typically have a specific gravity of 4.0 and so will float on water, at least until enough vesicles are saturated to cause them to sink. Expressed as density, pumice fragments typically weigh less than 1 g/cm3. Depending on moisture content, particle density, and particle size distribution, the bulk density of pumice typically ranges from 500 to 700 kg/m3. Typical bulk densities of cinder range from 700 to 900 kg/m3 for material used as lightweight aggregate while the bulk density of cinder used for highways and railroad ballast may be considerably higher. Hardness in pumice may refer to the glass vesicle walls, possibly including crystals or lithic fragments, or to the apparent hardness of the particle as a whole, which is more a measure of the strength of the vesicle structure. Pumice glass typically has a Mohs hardness of 5 to 5.5. A pumice particle may have a much lower apparent hardness and be easily cut with a knife or steel saw because the vesicle walls break readily. Pumice and cinder are primarily pyroclastic deposits formed as fragmental products of volcanic eruptions. Several classification - systems differing in various details have been proposed for pyroclasts and pyroclastic deposits based on particle size (Fisher, 1961, Schmid, 1981, Cas and Wright, 1988). Generally, particles >64 mm are referred to as blocks or bombs depending on their shape. Particles between 64 mm and 2 mm (4 mm in some schemes) are called lapilli and smaller particles are called ash. These names may be modified by compositional terms, for example pumice lapilli or scoria lapilli. Most commercial deposits are composed of fragments in the lapilli size range. In the United States, pumice fragments having one dimension of 5 cm or more are legally defined as block pumice. The procedures for acquiring pumice from federal land are determined in part by this definition and are described in a later section.

Jan 1, 1994

By W. M. Jr. Aubrey, R. L. Stone

INTRODUCTION Most metallic minerals and some industrial minerals have a relatively high specific gravity and most have at one time or another been concentrated by gravity methods. The principles of gravity concentration are straightforward, well documented and easy to understand, but in practice there are many pitfalls that await the engineer in the development of an integrated flowsheet. Gravity concentration equipment has a long history of use and there is a great diversity available. The equipment is capable of treating material over a broad size range, only falling off in efficiency in the very fine sizes. Gravity concentration is also inexpensive, generally free of environmental problems, and commercial equipment can process large tonnages of ore with a minimum of capital cost. As might be expected of an efficient and low cost process, the bulk of the tonnage quickly and inexpensively. Another obvious application is treating mineral deposits such as hematite and manganese ores that are sufficiently liberated after a minimum of crushing to allow production of a coarse concentrate that will meet market specifications. Except for hand picking and mechanical sorting, there is no competing process on coarse size material. Conversely, it is sometimes obvious that gravity concentration does not warrant consideration. Examples are ores that require very fine grinding to attain liberation, for ores where the minerals of interest have a gravity similar to the gangue, and ores that are strongly magnetic. Actually a mineral processing engineer may not know if gravity is the best way to concentrate an ore, but he should have little difficulty recognizing when gravity concentration deserves consideration based upon specific gravity differences and liberation gravity concentration has wide use. size. His challenge then is to At times its selection as the identify and test the applicable primary concentration process is processes, to develop a obvious. Low grade placer deposits metallurgical balance and flowsheet of tin, gold and beach sands usually for the best process, to estimate are only profitable because gravity production rate over the life of concentration is able to throw away the deposit and to make equipment

Jan 1, 1986

By D. E. Ranta, G. H. Giroux, A. W. Randall, D. A. Barr

Zinc-lead ores of the Pine Point District, Northwest Territories, Canada, are hosted in paleokarst cavities within a Middle Devonian carbonate barrier complex. Of the nearly 100 deposits found, most are irregularly distributed along two main regional stratigraphically controlled trends. The ores, which occur predominantly as open space filling, form deposits most of which average one million tonnes in size with an average grade of 10% combined zinc plus lead. Geological features related to karsting control not only distribution of deposits but also their shape, size and grade. The higher grade ore in these deposits generally occurs in a relatively small core area. Consequently, accuracy of reserve estimation is dependent on drill-hole density and understanding of karst geometry. Several case examples will be reviewed to demonstrate the relationship between shape, size and grade of deposit, geological reserves and drill-hole density, along with a discussion of geological ore reserve estimation methods.

Jan 1, 1992

By Darrell V. B. . McClarty

In 1996, Rio Algom, Denison Mines and the Elliot Lake Research Field Station (ELRFS) formed a consortium to implement a regional environmental information management system (REIMS) for the Elliot Lake area in Ontario, Canada. ELRFS is an affiliate of Laurentian University in Sudbury, Ontario, The discovery of uranium in the Elliot Lake region in post-World War II led to the development of 12 mines and 11 associated mills between 1955 and 1958. During the late 1980s, declining world demand for uranium, combined with the discovery of high-grade uranium ore in other areas of the world, made the Elliot Lake mines uneconomical. As a result, all area mines ceased opera¬tions by the end of 1996. The eight facilities and three tailings management areas operated by Denison Mines and Rio Algom&apos;s five mining waste management areas contain 150 Mt (165 million st) of potentially acid-generating tailings. The areas cover 13.2 km2 (3,265 acres) and receive drainage from an additional 13 km2 (3,212 acres). The primary objective of the joint initiative was to implement a personal-computer-based, regional, environmental-information management system for managing historical data and ongoing environmental programs in the Elliot Lake region. The Elliot Lake consortium decided it needed an information system with an integrated, process-oriented and requirements-driven approach to collect and manage the environmental information. Following a study of environmental information management systems currently used by the mining industry, the consortium decided to base REIMS on the "Envista" product. This is a commercially available, environmental information management system marketed by Envista Technologies of Saskatoon, Canada.

Jan 1, 1999

By P. T. Bissert, T. J. Lutz, J. A. Yonkey, G. T. Homce

"The National Institute for Occupational Safety and Health (NIOSH) has been researching refuge alternatives (RAs) since 2007. Refuge alternatives typically have built-in pressure relief valves (PRVs) to prevent the unit from reaching unsafe pressures. The Mine Safety and Health Administration (MSHA) requires that the PRVs vent the chamber at a maximum pressure of 1.25 kPa (0.18 psi, 5.0 in. H2O), or as specified by the manufacturer. To facilitate PRV testing, an instrumented benchtop test fixture was developed using an off-the-shelf centrifugal blower and ductwork. Relief pressures and flow characteristics were measured for three units: a modified PVC check valve, an off-the-shelf brass/cast iron butterfly check valve, and a commercially available valve that was designed specifically for one manufacturer’s steel pre-fabricated RA and has been adapted for use in built-in-place (BIP) RAs located at one mine. PRVs used in tent style RAs were not investigated. The units were tested with different modifications and configurations in order to check compliance with 30 CFR regulations. BACKGROUND The Mine Improvement and New Emergency Response Act of 2006 (Miner Act) (1) was enacted in the wake of three mine explosions/fires that claimed 19 lives that year. Intended to help improve underground coal mine accident preparedness, the MINER Act includes provisions that target mine safety issues in areas such as emergency response planning, adoption of new technology, training and education, and mine safety standards enforcement. Section 13 of the MINER Act specifically directed the National Institute for Occupational Safety and Health (NIOSH) to provide for research into the effectiveness and viability of refuge alternatives (RAs) for underground coal mines, and the Department of Labor to act on the results of such research as appropriate. These mandates culminated in the 2009 adoption of changes to 30 CFR mining health and safety regulations, requiring underground coal mines to provide mine emergency RAs and associated components, to provide a life-sustaining environment for persons trapped underground. Such RAs can be either self-contained mobile units or built-in-place (BIP) facilities. The regulatory changes also include provisions establishing requirements for the Mine Safety and Health Administration (MSHA) approval of RAs and their components, and among these provisions are numerous criteria for providing a safe breathable atmosphere under positive pressure within the RAs. One specific criterion for maintaining a safe RA atmosphere requires the inclusion of an air pressure relief valve that will activate at a maximum of 1.25 kPa (specified as 0.18 psi, or approximately 5.0 in H2O), or at a pressure as specified by the RA manufacturer, above mine atmospheric pressure in the RA (2)."

Jan 1, 2016

By Harold R. Kokal, Madhu G. Ranade

A metallurgical/flux is a substance that is added to combine with gangue (unwanted minerals) during ore smelting, with impurities in a molten metal, or with other additives in metal refining processes to form a slag that can be separated from the metal. Because slags are immiscible with the metallic melt and are of lower density, a separation of the slag and metal occurs if the viscosity and surface tension are of the proper values. The chemistries of slags are adjusted to provide the proper melting point, viscosity, surface tension, conductivity, specific heat, density, or chemical properties to effect the desired task. In addition to absorbing impurities from the metal, the purposes of the slag are to thermally insulate the metal bath, protect the molten metal from the atmosphere, and control the chemical potential of the system. Several excellent references on slags and metallurgical fluxes are available (Boynton, 1980, Lankford, Jr., et al., 1985, Turkdogan, 1983, Rosenqvist, 1974, Fine and Gaskell, 1984). The function of the slag might vary at different stages within a process prior to final melting. For example, the slag composition and behavior will change as materials descend in the iron blast furnace, or as they melt in the early stages of formation of steel- making slags. Selection of the chemistry for a slag might be influenced by factors outside the primary function as when blast furnace slags are used to make cement, rock wool insulation, or fertilizer supplements. Sometimes slags contain a sufficient amount of valuable recoverable elements to be sold as raw materials for other processes. Fluxes are often referred to as acid, basic, or neutral. Acid fluxes are those that generally form acids in water and bases are those that would generally form bases in water. Typical acid fluxes are silica, alumina, and phosphorus, although alumina can function as either an acid or base. Typical basic fluxes are lime and magnesia. Fluorspar, or calcium fluoride, is a neutral substance because it can be viewed as the reaction product of a base and an acid. The degree of acidity (ratio of acids to bases) or basicity (ratio of bases to acids) is often specified to characterize the slag chemistry for a particular system. The system might also be referred to as acid or basic depending on the choice of slag, for example, basic steelmaking uses slags with more bases (lime and magnesia) than acids (silica and alumina). Many forms of minerals and compounds have been used as fluxes depending on the process requirements, availability, costs, requirements for recycling of intermediate products, and environmental concerns. Because slags are most often mixtures of oxides and silicates, fluxes are usually oxides, carbonates (which decompose to oxides) and silicates. Slags comprising phosphates, borates, sulfides, carbides, or halides have also been used (Rosenqvist, 1974, Moore, 1981, Szekely et al., 1989). In ironmaking and steelmaking, some acidic components are sometimes added. In nonferrous processes slags and fluxes are acidic with silica as the primary component, and although the use of basic flux such as limestone or lime is not extensive, some amount is used to modify slag properties and some refining slags are lime based. The production of iron is accomplished by smelting of ores, pellets, and sinter in blast furnaces with subsequent refining of molten iron and scrap in oxygen-blown processes. The electric furnace is used to make steel, stainless steels, ferroalloys, and special alloys, whereas ferromanganese is often made in blast furnaces. Fluxes are used in all of these processes, and either limestone or lime is the major flux component with some dolomite, dolomitic lime, silica, alumina, and fluorspar being used. In ironmaking, the flux is added either by direct charging or through sinter and fluxed pellets. In steel refining by the basic oxygen process, flux is added as lime and dolomitic lime that are either charged as lumps or injected as fines. Some small amount of limestone is sometimes used. Fluorspar is often added as lumps or mixed with other fine materials in briquettes. Alumina is sometimes added to blast furnaces either by direct charging of sized lumps or through sinter. Typical acid fluxes are sand, gravel, quartz rock, used silica brick, or raw siliceous ore (Lankford, Jr., et al., 1985). Olivine, which is a magnesium-silicate mineral, has been added to iron blast furnaces to enhance removal of alkalis (Lankford, Jr., et al., 1985). Alumina in the form of bauxite, aluminiferous clay, and recycled alumina brick has been used as flux. Alumina can function amphoterically as either an acid or base, for example it can form aluminum silicate in high silica slags or calcium aluminate in lime-bearing slags (Lankford, Jr., et al., 1985). Limestone (calcium carbonate) and dolomite (magnesium-calcium carbonate), or fluxstones as they are sometimes called (Boynton, 1980), and their calcined forms, lime and dolomitic lime are the major basic fluxes. In the latter cases, the carbonates are de- composed in a kiln-type process to drive off carbon dioxide that might otherwise interfere with the subsequent smelting or refining process or require expensive forms of energy to effect the decomposition (e.g., by combustion of coke in the iron blast furnace). Limestone is considerably less expensive than lime because it is not calcined; however, lime is far more difficult to handle and reacts readily with water. Dolomite and dolomitic lime are used for their magnesia content. Fluorspar is a neutral flux often used as an additive in steel- making slags to improve fluidity, but it has also been used in combination with lime as a primary slag in electroslag refining (Duckworth and Hoyle, 1969). Fluorspar is available in several grades, with the lowest grade often used for steelmaking. When the price of fluorspar has risen, substitutes including aluminum smelting dross, borax, manganese ore, titania, iron oxides, silica sand, and

Jan 1, 1994

By David D. Rabb

Leaching or solution mining, a relatively simple and economical process for beneficiating metallic ores, is likely to find increasing application in the treatment of low-grade ores that are impractical to mine by any other means. This process may be carried out in two different ways: 1. Dump leaching, where the ore is moved from its original location to be leached at another site. 2. In situ leaching, where the ore is leached in place by introducing the leach solution at the top, letting it flow down through the ore under gravity, and then recovering it plus the dissolved metals it contains.

Jan 1, 1969

By John C. Wangaard

A method of raising by use of a cage has been used with considerable success at the Cary Mine, Hurley, Wisconsin, on the Gogebic Range. The Cary Mine is owned by the Odanah Iron Company, Pickands, Mather and Company, Managers. This method is known to have been used previously at Tennessee Copper and probably in other districts. The Cary Mine was engaged in deepening the main shaft from the 34th to the 37th level. To accomplish this, and to facilitate development, a ventilation shaft 930 feet north of the main shaft was sunk from the 34th to the 37th level and crosscuts were driven on the 35th, 36th and 37th levels to the main shaft location, These levels are at 200 foot verticalintervals. All of this work was done in granite and the majority of the workings were not timbered. The next step was to get a raise through from the 37th to the 36th level, and from the 36th to the 35th level, which would later be stripped to full shaft size. Several methods of raising were considered including double-compartment cribbed and two single raises interconnected at regular intervals, but the cage method was chosen as it appeared to be a safe and efficient operation. The method in general consists in the use of a drill hole between levels through which to pass a hoisting rope to raise and lower a light cage.

Jan 1, 1958

By Bruce F. Bohor

Silica sand has been mined in Illinois from the St. Peter Sandstone since the turn of the century, especially in the area around Ottawa on the Illinois River in the north-central part of the state. Production of this sand, consumed mainly by the glass and foundry industries but also sought after for many other uses, has grown with the economy, and last year&apos;s output in Illinois exceeded 4,000,000 tons. Such an important commodity was given the early attention of the Illinois State Geological Survey, and a very complete report was issued in 1928, authored by J. E. Lamar. The mining and processing of the sand has changed very little during the intervening 40 years, so that much of Lamar&apos;s data and descriptions are applicable today. More recently, the stratigraphy of the St. Peter Sandstone in north-central Illinois has become better known from the work of Willman and Payne (1942). The present authors have borrowed generously from Lamar&apos;s publication, and we wish to acknowledge the contribution of both of these studies to our work.

Jan 1, 1969

By K. A. Brame, L. G. Austin, R. S. C. Rogers

The breakage parameters of phosphate ore were determined by batch first-ordering grinding studies in a laboratory ball mill according to the Austin, Klimpel, and Luckie procedures. The results were scaled to five larger mills of 0.56, 0.82, 8.36, 4.41, and 5 m in diameter assuming equilibrium ball charges for the full-scale mills. The results were used to predict product size distributions and capacities for batch grinding in the smaller mills and open-circuit grinding in the larger mills. The predicted capacities were in approximate agreement with experimental values except for the 5-m diam mill. The Bond method gave capacity predictions that were 4570 to 150% too high.

Jan 1, 1987

By John S. Thayer, Frederick E. Brinckman, Kenneth L. Jewett, Gregory J. Olson

Interest and research in biorecovery of metals has focused mainly on cell-based metal leaching and precipitation. However, production of non-enzymatic metabolic products by microorganisms related to metals bioprocessing also deserves attention. For example, it is well known that biogenic inorganic (e. g. H2S04 ) and organic acids play a role in metal dissolution. There are other metabolic products of microorganisms which can catalyze useful metals transformations. These include methylated metabolites such as alkyl halides which can dissolve metals from ores and also reduce certain metal ions in solution to pure metallic particles. This paper describes some of our research on metal dissolution and precipitation by such metabolites. Examples include the production of high purity elemental metal particles of gold, platinum and palladium by volatile metabolic products.

Jan 1, 1989

By N. Finkelstein, D. A. Hinckfuss

The large and compact but simple Bougainville Copper Limited flotation circuit has been in operation for 3-1/2 years. Discussion of problem areas encountered since start-up and remedies that have been implemented or proposed, form the main basis of this paper. Full cur- rent operational data is also provided.

Jan 1, 1976

By Cathleen J. Webb, Arden D. Davis

Begun in 1992, an abandoned and inactive mine inventory in the Black Hills National Forest has resulted in a hazard ranking of the most severely affected sites. For purposes of the inventory, the Black Hills were divided into three main regions: the northern Black Hills, with primarily gold mines; the central Black Hills, with pegmatite mines and some gold mines; and the southern Black Hills, with primarily uranium mines. A computerized data base has been developed along with standard forms for field crews. The forms were designed to provide maximum compatibility with other abandoned mine inventories on various federal and state lands. Measures recommended for the most hazardous and heavily affected sites include regrading of unstable slopes, fencing of open shafts, and remediation of the most severe acidic mine drainage problems. Specific examples are illustrated where remediation and safety measures were recommended or have been implemented. The vast majority of the sites, however, needed little or no remedial action.

Jan 1, 1995

By R. Asmatulu

According to Darcy&apos;s law, the rate of filtration should increase with increasing pressure drop across a filter cake. In centrifugal filtration, the driving pressure is created by the centrifugal forces applied in the free water on the surface of a filter cake. However, the pressure drop can become negative when the free water surface disappears, which makes it difficult to achieve low cake moistures. In hyperbaric centrifugal filtration, this problem is overcome using air pressure to restore the pressure differential. In the present work, various mineral and coal fines have been subjected to hyperbaric centrifugal filtration tests. The laboratory tests show that the moistures of various mineral fines, such as copper and zinc concentrates, phosphate, talc, kaolin clay, and precipitated calcium carbonate, can be reduced substantially below that achieved by conventional centrifuges. Similar promising results have also been obtained with various coal fines in laboratory and pilot-scale test programs and in full-scale plant demonstrations.

Jan 1, 2012

By Ing. E. h. Martin Herrenknecht

The paper will describe a number of developments and innovations now in use in microtunnelling machines. These include the use of fuzzy logic steering systems, the proven ability to successfully undertake complex curved microtunnel drives, the ability to complete ultra long drives using microtunnelling techniques, and machines with access to the face of the machine from inside the machine. The ability to tunnel in relatively hard rock utilizing a rock head with back loaded cutters changeable from inside the microtunnel machine and the ability to utilize microtunnel machines in multi modes, such as hard rock mode, “open” mode, EPB mode, and slurry mode with the same base machine again with access to the face of the machine will be described. In addition, the latest computer technology gives the operator “full visualization” of machine functions together with the ability to data log machine operating parameters. Reference will be made to a number of projects worldwide recently completed or under way where these innovations have successfully been utilized.

Jan 1, 1999

By Frank R. (Original by) Barnako

Coal mining historically has been a hazardous occupation but, in recent years, tremendous progress has been made in reducing accidental coal mine deaths and injuries. The purpose of this chapter is to discuss the basic principles of accident prevention as they are related to coal mining. Accident prevention fundamentals are no different for coal mining than for any other type of work. The fundamentals apply to all industries. Construction workers may be struck by falling tools and materials, and miners may be struck by falling slate and coal. Sailors may be trapped by shipboard fires, and miners may be trapped by mine fires. Railroad brakemen may lose hands and fingers positioning couplers, and miners may lose hands and fingers positioning couplers. Many other examples could be cited, but the point is that accidents that happen in coal mines are basically similar to accidents that happen in other industries. Thus, the basic principles for preventing accidents apply in coal mining as they do in any other type of work.

Jan 1, 1981